In a big code porting project recently I had to move a number of unit tests from one class over to another. I didn't give it a second thought beyond that until it came to running the build. Compilation was successful, however JUnit execution failed on the tests I moved. Odd. At first I thought maybe I accidentally changed some code, but no, all the code was the same. Then I realised what the problem was.

The class that I moved these tests from was written for JUnit 4.x and used the @Test annotation. However the class that originally had these tests was written for JUnit 3.x and was extending the TestCase class and no annotations.

This meant that my perfectly legitimate test case like that looked like this...

JUnit 4.x test case

@Test(expected = MyException.class)

public void test_myExceptionThrowsTest1() throws MyException {

/* some code here that throws MyException */

}

...would always cause my build to fail when executed inside a test case designed for use with JUnit 3.x like this...

JUnit 3.x test case

public class MyTest extends TestCase {

...

}

The solution was of course not to mix the two approaches. In my case, I removed the 'extends TestCase' from the class and added @Test annotations to every other test case inside it. Once that was done, all my tests were passing again.